The manufacture of multiple glazed window units is a comparatively old and well developed art. It is commonplace to use aluminum and steel hollow spacers inserted in the interior of such windows in sealing relation between the opposed glass panes.
Plastic spacers, including pultruded fibreglass spacers are also known. However, many of the prior art constructions are expensive to manufacture, and many of the metallic ones provide a thermal bridge located on the innermost side of the seal and directly joining one glass inner face to the opposed glass inner face at an exposed location where a high thermal gradient exists. Under extremes of temperature that may be comparatively commonplace in northern areas of the United States, Canada, Scandinavia and Russia, with outside temperatures close to zero Fahrenheit and below, the effects of such thermal bridging may be to create a frost line along edge portions of the innermost pane adjacent the thermal bridge, to cause moisture precipitation or frost formation on the glass. Internal precipitation of moisture between the glass panes also can occur, which can lead ultimately to staining and discoloration of the glass, and of the peripheral seal, between the panes.
Certain aspects of the prior art are well illustrated by reference to prior patents, as follows:
U.K. Patent Application GB 2,077,834; Published Dec. 23, 1981, Albert. this illustrates a pair of hollow metallic sections in mutually nested, internally connected relation, the inner section being provided to abate noise transfer.
Canadian Patent 1, 008,307 Apr. 12, 1977, Berdan. This illustrates roll forming a hollow aluminum spacer section having a lip and groove joint on the innermost face thereof to aid flexibility.
U.S. Pat. No. 2,993,242, July 25, 1961, Leisibach. This illustrates the provision of metal spacer sections of H, U, T and other profile forms.
Germany: Offenlegungsschrift 2,730,264, Jan. 25, 1979, Jacobs. This illustrates various hollow tube sections and combined sections, with various plastic seals and separators.
U.S. Pat. No. 4,268,553, May 19, 1981, Marzouki et al. This shows a hollow rectangular section with rolled tongue and groove joint having a superposed plastic cap isolating the window space.
U.S. Pat. No. 4,222,213, Sept. 16, 1980, Kessler. This shows a hollow, generally rectangular metal section with a gapped inner flange and a plastic cap enclosing the top and sides of the section and protruding within the gapped flange of the section, as a perforated spacer.
U.S. Pat. No. 4,057,945, Nov. 15, 1977, Kessler. Similar to 213 above with the plastic cap forming two separate halves.
U.S. Pat. No. 4.113,905 Sept. 12, 1978, Kessler. This shows a hollow metal or plastic spacer with a foamed casing thereabout.
U.S. Pat. No. 3,971,178, July 27, 1976, Mazzoni et al. This shows a composite spacer with a gapped metal section containing a desiccant, with a communicating inner peripheral slot.
U.S. Pat. No. 4,658,553, Apr. 21, 1987, Shinagawa. This shows a thermoplastic hollow spacer section with a desiccant, and a communicating inner peripheral slot.
Other aspects of prior art seal constructions are shown in the following listed U.S. Pat. Nos.
U.S. Pat. No. 2,125,372 Aug. 2, 1938, Fox
U.S. Pat. No. 2,563,378 Aug. 7, 1951, Schnee
U.S. Pat. No. 2,838,809 June 17, 1958, Zeolla et al
U.S. Pat. No. 2,838,810 June 17, 1958, Englehart et al
U.S. Pat. No. 3,026,582 Mar. 27, 1962, Bayer
U.S. Pat. No. 3,261,139 July 19, 1966, Bond
U.S. Pat. No. 3,919,821 Nov. 18, 1975, Goetz
U.S. Pat. No. 4,171,601 Oct. 23, 1979, Gotz
U.S. Pat. No. 4,576,841 Mar. 1986, Lingemann
The prior art is characterized by many spacer embodiments which serve as thermal bridges, or which suffer from drawbacks such as high cost, complexity, reliance for sealing on gas permeable materials, etc.
A further form of synthetic spacer comprises a "swiggle strip" as sold by the Tremco Corporation, having desiccant embedded therein. Desiccant activity in controlling humidity can be impaired and the installation of the soft, pliable spacer requires use of a special purpose machine.